Schedule-induced drug ingestion appears to be an inexpensive, uncomplicated method of inducing voluntary drug ingestion in experimental animals. This method avoids the trauma of painful injections, or surgical interventions which undoubtedly leave residual effects in the animal (e.g., pain) which may be confounded with drug effects. On the other hand, however, other factors which are idiosyncratic to this model play an important role in modulating drug ingestive behavior. These are: palatability of drug solution, and conditioned aversion/preference for the drug solution arising from the pharmacological properties of the drug. Significant differences in drug ingestion were obtained in experimental rats, depending on type of drug, whether morphine (an opiate), chlordiazepoxide (a mild tranquilizer) or meth-amphetamine (a stimulant). Palatability and conditioned aversion were found to influence drug ingestion in this schedule-controlled behavior. Moreover, regardless of amount of drug consumed during daily sessions, rats showed little home cage consumption when water was also available. Session length and frequency are probably important factors in drug-seeking behavior outside of the experimental session, and these will be investigated.